Semiconductor element having a polymeric protective coating and glass coating overlay

ABSTRACT

A multilayer passivation-encapsulation for a semiconductor element is provided by a suitable polymer layer disposed on the device and overcoated with a glass layer for hermeticity.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This patent application is a continuation-in-part of my co-pendingpatent application Ser. No. 601,839, filed on Aug. 4, 1975, now U.S.Pat. No. 4,017,340, and assigned to the same assignee as thisapplication.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to protective coating materials for semiconductorelements.

2. Description of the Prior Art

Heretofore, some prior art methods provide coating at least preselectedexposed surface areas of semiconductor elements with electricallyinsulating oxide materials. Such coatings are thin layers and havevirtually no resistance to mechanical abrasion and require relativelyexpensive processing equipment. In almost all instances a second and athicker coat of a protective coating material is provided to protect theinitial electrically insulating material. Silicone greases, varnishes,rubbers and resins which are employed as the overcoating of protectivematerial have been found lacking in desirable physical characteristics.

Robert R. Shaw in U.S. Pat. No. 3,615,913, granted on Oct. 26, 1971,teaches the employment of a coating of a cured, protective coatingmaterial selected from the group consisting of polyimides, andpolyamide-polyimides disposed on exposed end portions of at least oneP-N junction to provide passivation thereof. Although these materialsexhibited good abrasion resistance properties, the passivationrequirements of the semiconductor element still required improvements tobe made thereto.

There is currently wide spread use of oxide/glass layers for passivationand encapsulation of semiconductor devices where device stability andlong life are important considerations. However, if the glassy layermust be applied after aluminum metallization, (a wide spreadrequirement), the choice of suitable glass systems is severelycircumscribed by a maximum permissible application temperature of ˜ 577°C. This restriction is set by the alumina-silicon eutectic and must becarefully observed in all processing operations following aluminizationof the silicon.

Several glass coating methods are currently in use. These includechemical vapor deposition (CVD), glass frits, and spin-on glass formingalcoholates. The last method is only capable of forming very thinlayers, of the order of 2000A, of glasses which tend to be more reactivethan desirable and, therefore, are of restricted utility in packaging.Glass frits are widely used in packaging but are not usually employedfor surface passivation because of difficulties in formulating glasseswith an adequate expansion match to silicon, and which are at the sametime suitable passivants and chemically stable. CVD methods permitadequate thickness, a wide choice of composition, expansion matching,etc. but difficulties in controlling sodium contamination in CVDreactors have made it difficult to obtain acceptable passivation layersby direct deposition onto bare silicon. This method is, therefore,usually restricted to use as an overcoating of SiO₂ and metallizationlayers. None of these methods in their current state of development isconsidered capable of providing a reliable passivation/encapsulationmethod for large thyristors and other power semiconductor devices.

The processing of such devices usually requires surface passivation ofbare silicon p-n junctions with aluminum contacts already in place onthe silicon. Thus the above-mentioned temperature restrictions onprocessing apply. Additionally, however, one must concern oneself withthe surface charge of the passivation layer when it is directly appliedto bare silicon. Such charge can be fixed and positive as in the case ofa clean grown thermal oxide, or mobile, e.g., when due to the presenceof sodium ion contamination of the oxide. Certain proprietary glasscompositions give a negative fixed charge when applied to silicon.

Within limits, on some devices, an appropriate surface charge can bebeneficial. For example, in the case of a P^(+N) diode under reversebias conditions, a negative surface charge will tend to deplete thesurface of the n-type material, spread the depletion layer near thesurface and hence lower surface electric field thus suppressing surfacebreakdown. On a P N+ diode, positive surface charge could have a similarbeneficial effect if certain limits are not exceeded. Too much surfacecharge can cause surface inversion and channeling with a concommittantincrease in surface leakage which is intolerable.

In many power devices, e.g., such as high voltage D.C. thyristors, theedges of the device are tapered or beveled in order to reduce surfacefields and suppress surface breakdown. Since such devices are designedto block in both forward or reverse directions when not turned on by thecontrol gate, one encounters the situation that on alternate half cyclesmaximum surface fields can exist on either side of lightly doped p-njunctions comprising the device and any surface charge will bedeleterious favoring surface breakdown in either forward or reverseblocking conditions.

In such cases the most favorable surface coating is one which is chargeneutral or nearly so. Currently, there are no known passivation coatingsinvolving glasses or silicon oxides capable of giving such a desiredcharge neutral surface.

In the co-pending patent application it was my belief that apolyimide-silicone copolymer material, overlaid with a chemical vapordeposited glass layer was most desirable. However, it has beendiscovered that in some instances the silicone material need not bepresent.

Therefore, it is an object of this invention to provide a new andimproved passivation process for semiconductor elements which overcomesthe deficiencies of the prior art.

An object of this invention is to provide a semiconductor element havinga passivation coating embodying at least one glass layer overcoating apolyimide polymer or a polyimide-silicone copolymer material layer.

Other objects of this invention will, in part, be obvious and will, inpart, appear hereinafter.

SUMMARY OF THE INVENTION

In accordance with the teachings of this invention, there is provided anew and improved semiconductor element comprising a body ofsemiconductor material having at least two regions of opposite typeconductivity. A P-N junction is disposed between, and formed by theabutting surfaces of, each pair of regions of opposite typeconductivity. An end portion of at least one P-N junction is exposed ata surface of the body.

A layer of a protective coating material is disposed on a selected areaof the body including the at least one exposed P-N junction thereat. Thematerial of the protective coating layer adheres to the surface of thebody, has excellent abrasion resistance and is capable of withstandingselected elevated temperature excursions for a period of time. Thematerial is substantially free of outgassing during the temperatureexcursion and has a desirable glass transition temperature. At least onelayer of a glass-like material is deposited on the protective coatingmaterial. The glass material has good adhesion to the material of theprotective coating layer and has a coefficient of thermal expansion wellmatched with that of the semiconductor material of the body. A secondglass layer may be deposited on the first glass layer. The glassmaterial forms a hermetic seal for the surface of the element that itcovers. Preferably the glass layers are chemically vapor deposited onthe surface.

A layer of borosilicate glass having about 19% boron is suitable for abody of silicon semiconductor material. The protective coating materialmay be a polyimide, polyimide-polyamide or a polyimide-siliconecopolymer, which adheres well to both the silicon and to theborosilicate glass. Such a suitable material is either one of thefollowing:

1. the reaction product of a silicon-free organic diamine and an organictetracarboxylic dianhydride in a suitable organic solvent which whencured, yields a polymer having recurring structural units of thefollowing formula: ##STR1## wherein R" is a tetravalent organic radical,Q is a divalent silicon-free organic radical which is the residue of anorganic diamine and m is an integer greater than 1 and preferably from10 to 10,000 or more.

2. the reaction product of a silicon-free organic diamine, an organictetracarboxylic dianhydride and a polysiloxane diamine, in a suitableorganic solvent, which when cured, yields a copolymer having recurringstructural units of formula I and with from 5 to 50 mol percentintercondensed structural units of the following formula II: ##STR2##wherein R is a divalent hydrocarbon radical, R' is a monovalenthydrocarbon radical, R" is a tetravalent organic radical, x is a wholenumber equal to at least 1 and advantageously from 1 to 8 and as high as1 to 10,000 or more, n is an integer which is the same as, or differentfrom m of formula I and is greater than 1 and preferably from b 10 to10,000 or more.

3. a blend of the polyimide material of Formula I and the polyimidematerial of Formula II in such molar proportions that the structuralunits of the latter are within the range of from 5 to 50 mol percent ofthe units based on the total molar concentration of the units of FormulaII and the units of Formula I.

DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are side elevation views, in cross-section, ofsemiconductor elements embodying the novel structure of this invention.

DESCRIPTION OF THE INVENTION

With reference to FIG. 1, there is shown a semiconductor element 10comprised of a body 12 of semiconductor material. The body 12 isprepared by suitable means, such, for example, as by polishing andlapping to parallelism two opposed surfaces 14 and 16. The body 12 hastwo or more regions of opposite type conductivity and a P-N junctionformed by the abutting surfaces of each pair of regions of opposite typeconductivity. The end portion of at least one P-N junction is exposed ina surface of the body 12. The body 12 comprises a suitable semiconductormaterial such, for example, as silicon, silicon carbide, germanium,compounds of Group II and Group VI elements.

In order to more fully describe the invention and for no other purposes,the body 12 will be described as being comprised of siliconsemiconductor material having five regions of conductivity and four P-Njunctions. Such a configured element 10 may function as a thyristor.Therefore, the body 12 has regions 18 and 20 of P-type conductivity,region 19 of P^(+-type) conductivity and regions 22, 24, and 26 ofN-type conductivity. P-N junctions 28, 30, 32 and 34 are formed by theabutting surfaces of the respective pairs of regions 18 and 22, 22 and20, 20 and 24, and 20 and 26 of opposite type conductivity.

One means of controlling the surface electric field on such a controlledrectifier is to contour the side surface 36 after affixing the partiallyprocessed body 12 to a large area contact, or support electrode, 38 by alayer 40 of a suitable ohmic electrical solder. Electrical contacts 42and 44 are affixed to the respective regions 24 and 26. As illustrated,the contouring of the surface 36 results in the well known "doublebevel" surface.

Referring now to FIG. 2, there is shown a semiconductor element 50embodying a double positive bevel configuration for controlling surfaceelectric field. All items denoted by the same reference numbers as thosein element 10 of FIG. 1 are the same, and function in the same manner,as the corresponding item in element 10. The element 50 functions as athyristor for the configuration illustrated.

Regardless of the method employed to control the surface electric field,selected end portions of at least some of the P-N junctions are exposedat surface areas of the body 12. It is necessary therefore to apply asuitable material to protect the exposed end portions of the P-Njunctions.

A layer 46 of a protective coating material is disposed on at least thesurface 36 and the exposed end portion of at least the P-N junctions 28and 30. It is desirable that the material of the layer 46 adhere to thesurface 36 as well as to the material of the layer 44 and the contact,or support electrode 38. The material of the layer 46 must also becapable of withstanding an elevated temperature for periods of timenecessary to deposit glass materials by chemical vapor deposition orother techniques upon the layer 46. Such glass materials for theover-layer are CVD deposited glasses, or glass frits and glass appliedby spin application. Additionally, the material of the layer 46 must becapable of providing, when cured, an adherent bond between the glasslayer and itself and should exhibit good abrasion resistance, as well asresistance to the chemical reagents utilized in completing thefabrication of the element 10. Further, the material comprising thelayer 46 must not exhibit any outgassing of the polymer duringdeposition, or formation, of the glass layer 48. Additionally, thematerial of layer 46 should have a low glass transition temperature soas not to cause too great a strain to be retained in the layer 46 whichmay cause the layer 46 to lift away from the surface 36. A desirablerange of glass transition temperature is from about 150° C. to 350 ° C.,with a preferred value of ˜ 200° C.

A protective coating material such, for example, as a polyimide or apolyimide-silicone copolymer, the composition of which is to bedescribed later has been found to be such a desirable material whendisposed on at least the surface 36 and the exposed end portion of atleast the P-N junctions 28 and 30.

The protective coating material may be disposed on the surface 36 as apolymer precurser dissolved in a suitable solvent. Upon heating, thesolvent is evaporated and the protective coating material of the layer46 is polymerized in situ on the surface 36 and the end portion of atleast one P-N junction. Preferably, the material of the layer 46 isapplied to the preselected surface area of the surface 36 of the body 12as a solution of a soluble polymeric intermediate. Application of thematerial to at least the surface 36 of the body 12 is by such suitablemeans as spraying, spinning, brushing and the like. The body 12 with theapplied protective coating material is then heated to convert theresinous soluble polymer intermediate to a cured, solid, and selectivelyinsoluble material.

One of two suitable materials for comprising the layer 46 and meetingthe aforesaid requirements is the reaction product of a silicon-freeorganic diamine and an organic tetracarboxylic dianhydride in a suitableorganic solvent to yield a polymer having recurring structural units ofthe following formula: ##STR3## wherein R" is a tetravalent organicradical, Q is a divalent silicon-free organic radical which is theresidue of an organic diamine and m is an integer greater than 1 andpreferably from 10 to 10,000 or more.

The second of the two suitable materials is the reaction product of asilicon-free organic diamine, an organic tetracarboxylic dianhydride anda polysiloxane diamine, in a suitable organic solvent to yield acopolymer having recurring structural units of formula I and with from 5to 50 mol percent intercondensed structural units of the followingformula II: ##STR4## wherein R is a divalent hydrocarbon radical, R' isa monovalent hydrocarbon radical, R" is a tetravalent organic radical, xis a whole number equal to at least 1 and advantageously from 1 to 8 andas high as 1 to 10,000 or more, n is an integer which is the same as, ordifferent from m of formula I and is greater than 1 and preferably from10 to 10,000 or more.

The above-mentioned polyimide-silicone random or block copolymers can beprepared by effecting reaction, in the proper molar proportions, of amixture of ingredients comprising a diaminosiloxane of the generalformula: ##STR5## a silicon-free diamino compound of the formula:

    NH.sub.2 --Q--NH.sub.2                                     IV.

and a tetracarboxylic acid dianhydride having the formula ##STR6##wherein R, R', R", Q and x have the meanings given above.

Alternatively, a polysiloxane-imide composition may be used withcomparable effectiveness by blending together a polyimide composedsolely of recurring structural units of Formula I with a polyimidecomposed solely of recurring structural units of Formula II employingthe polyimide of Formula II in such a molar proportion that thestructural units of the latter are within the range of from 5 to 50 molpercent of said units based on the total molar concentration of theunits of Formula II and the units of Formula I.

It will be recognized that the ultimate polyimide siloxane compositionused in the practice of this invention will consist essentially of theimido structures found in Formulas I and II. However, the actualprecursor materials resulting from the reaction of the diamino-siloxane,the silicon-free organic diamine and the tetracarboxylic aciddianhydride will initially be in the form of a polyamic acid structurecomposed of structural units of the Formulas: ##STR7## where R, R', R",Q, x, m and n have the meanings given above.

The diamino siloxanes of Formula III which may be used in the practiceof the present invention include compounds having the followingformulas: ##STR8## and the like.

The diamines of Formula IV above are described in the prior art and areto a large extent commercially available materials. Typical of suchdiamines from which the prepolymer may be prepared are the following:

m-phenylenediamine;

p-phenylenediamine;

4,4'-diaminodiphenylpropane;

4,4'-diaminodiphenylmethane;

4,4'-methylene dianiline;

benzidine;

4,4'-diaminodiphenyl sulfide;

4,4'-diaminodiphenyl sulfone;

4,4'-diaminodiphenyl ether;

1,5-diaminophthalene;

3,3'-dimethylbenzidine;

3,3'-diamethoxybenzidine;

2,4-bis(βamino-t-butyl)toluene;

bis(p-βamino-t-butylphenyl)ether;

bis(p-β-methyl-o-aminopentyl)benzene;

1,3-diamino-4-isopropylbenzene; 1,2-bis(3-aminopropxy)ethane;

m-xylylenediamine;

p-xylylenediamine;

bis(4-aminocyclohexyl)methane;

decamethylendiamine;

3-methylheptamethylenediamine;

4,4-dimethylheptamethylenediamine;

2,11-dodecanediamine;

2,2-dimethylpropylenediamine;

octamethylenediamine;

3-methoxyhexamethylenediamine;

2,5-dimethylhexamethylenediamine;

2,5-dimethylheptamethylenediamine;

3-methylheptamethylenediamine;

5-methylnonamethylenediamine;

1,4-cyclohexanediamine;

1,12-octadecanediamine;

bis(3-aminopropyl)sulfide;

N-methyl-bis(3-aminopropyl)amine;

hexamethylenediamine;

heptamethylenediamine;

nonamethylenediamine;

and mixtures thereof. It should be noted that these diamines are givenmerely for the purpose of illustration and are not considered to be allinclusive. Other diamines not mentioned will readily be apparent tothose skilled in the art.

The tetracarboxylic acid dianhydrides of Formula V may further bedefined in that the R" is a tetravalent radical, e.g., a radical derivedfrom or containing an aromatic group containing at least 6 carbon atomscharacterized by benzenoid unsaturation, wherein each of the 4 carbonylgroups of the dianhydride are attached to a separate carbon atom in thetetravalent radical, the carbonyl groups being in pairs in which thegroups in each pair are attached to adjacent carbon atoms of the R"radical or to carbon atoms in the R" radical at most one carbon atomremoved, to provide a 5-membered or 6-membered ring as follows: ##STR9##Illustrations of dianhydrides suitable for use in the present invention(with their reference designated in parenthesis) include:

pyromellitic dianhydride (PMDA);

2,3,6,7-napthalene tetracarboxylic dianhydride;

3,3',4,4'-diphenyl tetracarboxylic dianhydride;

1,2,5,6-napthalene tetracarboxylic dianhydride;

2,2'3,3'-diphenyl tetracarboxylic dianhydride;

2,2-bis(3,4-dicarboxyphenyl)propanedianhydride;

bis(3,4-dicarboxyphenyl)sulfone dianhydride;

2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPAdianhydride);

2,2-bis[4-(2,3-dicarboxyphenoxy)phenyl]propane dianhydride;

benzophenone tetracarboxylic acid dianhydride (BPDA);

perylene-1,2,7,8-tetracarboxylic acid dianhydride;

bis(3,4-dicarboxyphenyl)ether dianhydride, and

bis(3,4-dicarboxyphenyl)methane dianhydride

and aliphatic anhydrides such as cyclopentane tetracarboxylicdianhydride, cyclohexane tetracarboxylic dianhydride, butanetetracarboxylic dianhydrides, etc. The incorporation of otheranhydrides, such as trimellitic anhydride, to make amide-imide-siloxanepolymers is not precluded.

Application of the random or block copolymers or blends of polymers in asuitable solvent (including, for example, N-methylpyrrolidone,N,N-diamethylacetamide, N,N-dimethylformamide, etc.) alone or combinedwith nonsolvents, to the substrate material may be by conventional meanssuch as dipping, spraying, painting, spinning, etc. The block or randomcopolymers or blends of polymers may be dried in an initial heating stepat temperatures of about 75° to 125° C. for a sufficient time frequentlyunder vacuum to remove the solvent. The polyamic acid is then convertedto the corresponding polyimide-siloxane by heating at temperatures ofabout 150°-300° C. for a sufficient time to effect the desiredconversion to the polyimide structure and final cure.

A preferred curing cycle for materials of the above general formula isas follows:

(a) from 15 to 30 minutes of from 135° C. to 150° C. in dry N₂.

(b) from 15 to 60 minutes at about 185° C. ±10° C. in dry N₂.

(c) from 1 to 3 hours at about 225° C. in vacuum.

Alternately, it has been found that one may be able to cure the coatingmaterial in other atmospheres such, for example, as air for ease ofcommerical application of this invention.

Sufficient material is applied to the surface 36 to provide a layer 46the thickness of which is from 0.1μm to 100 microns. The minimumthickness is determined by the requirement that the cured materialprevent the penetration of glass through the layer 46 to the silicon ofthe surface 36.

Alternately, one may employ the polymer material of Formula I withoutthe silicone material. It is known that the addition of the siliconematerial of the general Formula II increases the adhesive properties ofthe material of layer 46 as well as the corona resistance thereof.However, I have found that sometimes the polyimide material of thegeneral Formula I is sufficient for some device applications. I havefound that I can form the glass layer 48 over this polyimide material aswell and achieve excellent results. However, in each instance it ispreferred that the material of the layer 46 be capable of withstandingabout 450° C. for up to 20 to 30 minutes, as required, in normal deviceprocessing during manufacture.

Other suitable protective coating materials of polyimides, polyamides,polyimide-polyamides, and methods for making the same, all of which mayembody poly-siloxanes as required, are described further in U.S. Pat.Nos. 3,325,450, 3,553,282, 3,598,784 and 3,740,305 which by referenceare made part of the disclosures of the instant application.Additionally, polyimides, polyamides and polyimide-polyamides which willat least adhere to the material of the contacts 44 and 38 and withstandthe glass deposition temperature are also suitable for comprising thelayer 46. Preferably, any polymer material employed should adhere to thesemiconductor material and its metallized areas.

The layer 48 of glass is disposed on the layer 46 by any suitable meansknown to those skilled in the art. Such suitable means includes thedeposition of a glass frit layer of suitable thickness on the layer 46and thereafter forming the layer 48 by heating to an elevatedtemperature for a given time. In a similar manner, the glass may beformed by applying the glass on the layer 46 by a "spin on" techniquefollowed by a subsequent heat treatment. Preferably the layer 48 ofglass is deposited on the layer 46 by chemical vapor deposition. Thelayer 48 has a thickness of from 1μm to about 15μm. In the preferreddeposition process, the coated wafers, elements or devices 12 aredisposed within a chemical vapor deposition reactor and heated to theglass deposition temperature in an inert atmosphere. An appropriate gasmixture is introduced into the reactor and the layer 48 of glass grownor deposited on the layer 46. Suitable glasses to be vapor deposited arephosphosilicate and borosilicate glasses. For example, a gaseous mixtureof diborane, silane and oxygen at a temperature of about 400° C. ± 50°C. produce a layer 48 of borosilicate glass. A borosilicate glasscomprising from 15 to 25 mol percent B₂ O₃ is desirable. A preferredvalue for B₂ O₃ in the glass is 19 ± 2 mol percent. This preferred rangeof B₂ O₃ in the glass is desirable to achieve a glass layer 48 thethermal expansion coefficient of which matches that of the silicon body12 quite well. The glass deposition process is practiced for asufficient time to provide a thickness of from 1μm to 10μm for the layer48. A preferred thickness is 3μm.

Alternately a mixture of phosphine, silane and oxygen gases provides alayer 48 of phosphosilicate glass. The temperature of chemicaldeposition of the same is approximately 325° C. - 475° C. Other suitableglass application processes embody the use of glass frits and spin-onglass forming alcholates.

In order to assure better resistance to chemical attack and furtherreduce moisture permeability the two layers 46 and 28 can be overcoatedwith a second glass layer 49. The layer 49 preferably is silox orsilicon dioxide deposited at a temperature of about 400° C. ± 50° C. Theprocess is practiced for a sufficient time to provide a thickness forthe layer 49 of from 1000A to 5000A. A preferred thickness is 2000A.

In order to illustrate the teachings of this invention, deposits asdescribed have been applied to single crystal silicon semiconductormaterial, about 2 inches in diameter in the manner previously describedin this specification. A solution of the polymer precurser in the formof the polyamic acid form dissolved in N-methyl-2-pyrrolidone containing25% solids by weight was disposed on the surface of the silicon wafer.

The polymer precurser solution was formed by reacting benzophenonetetracarboxylic acid dianhydride with methylene dianiline andbis(γ-aminopropyl)tetramethyldisiloxane, the latter two diaminematerials being present in the molar ratio of 70:30. The reaction wascarried out at a temperature of less than 50° C. and using suitablypurified and dried materials to favor a large molecular weight polymer.

The protective coating material was cured in three stages of heating.Each coated device or wafer was heated to a temperature of 135° C. ± 5°C. for 20 minutes in an atmosphere of dry nitrogen gas. At thecompletion of this process time, the temperature was raised to 185° C. ±5° C. and the devices held at temperature in dry nitrogen gas for 30minutes. Upon completion of this process step, the devices were removedto a vacuum oven and heated to an elevated temperature of about 225° C.± 5° C. for from 1 to 3 hours. The devices were removed from the ovenand placed on a susceptor in a chemical vapor deposition reactor.

The devices were heated to an elevated temperature of 450° C. ± 5° C. inan atmosphere of nitrogen. When observed to be at temperature a gasmixture of diborane, silane and oxygen was then introduced into thereactor and caused to flow over the coated devices. The gas flow ratiowas as follows:

    ______________________________________                                        Diborane   13.5   cc/min, (1.05% in Argon)                                    Silane     450  cc/min. (5.1% in Argon)                                       Oxygen     >600 cc/min,                                                       ______________________________________                                    

The reaction was continued for about 6 minutes and the diborane gas wasturned off but the other gas flows were continued for another two andone half minutes. The reaction process was then stopped and the devicescooled to room temperature in ˜5 minutes.

A visual examination of the devices revealed the glass layers to be ofexcellent quality. The glass coating was homogeneous and featureless.

The coated devices exhibited excellent resistance to moisturepermeability. Additionally, the glass prevented the cured copolymermaterial from being attacked by the chemicals employed in furtherprocessing of the device.

Further examination showed the cured organic copolymer material toadhere tenaciously to both the silicon of the device and to theborosilicate glass deposited thereon. The thickness of the curedcopolymer was measured and found to be 3 micrometers. The thickness ofthe borosilicate layer, when measured, was 4000A and that of the siloxlayer 2000A.

As illustrated by the above example, the novel device process of thisinvention provides a possible means of eliminating the presentlyemployed hermetic packages. This is a significant reduction in theoverall cost of the device as sold commercially.

Other advances achieved by the novel devices and processing techniquesincludes a significant reduction in surface charge by use of the polymerpassivation film while retaining the barrier properties of glass as theouter hermetic layer. In contrast, glass disposed directly on thesilicon surface introduces alkali ions, particularly sodium ions, whichare free to contaminate the surface of the device. Because of the highelectric field which exist in the vicinity of a p-n junction, the ionsmove about the surface and cause current leakages which degrade thedevice. Additionally, the glasses of the protective coatings causesurface charges. These surface charges vary the depletion layer shapenear the surface upon which they are dispersed on the devices alteringsurface electric field which can favor voltage breakdown of the devicesat the surface so affected.

Therefore, the use of applicant's novel passivation coating enables oneto have a neutral charge coating material on the device surface.Additionally, the coating has excellent adhesion properties relative toboth the semiconductor material and the glass disposed on the coating.Chemical vapor deposition of the glass onto the organic copolymercoating is preferred as the composition of the glass can be readilycontrolled and/or varied during the deposition process.

I claim as my invention:
 1. A semiconductor element comprising:a body ofsemiconductor material having at least two regions of opposite typeconductivity and a P-N junction disposed between, and formed by theabutting surfaces of, each pair of regions of opposite typeconductivity; an end portion of at least one P-N junction exposed at asurface of the body; a layer of a protective coating material disposedon the exposed end portion of the at least one P-N junction; theprotective coating material is a polymer which is, when cured, oneselected from the group consisting of the reaction product of asilicon-free organic diamine and an organic tetracarboxylic dianhydride,a silicon-free organic diamine, an organic tetracarboxylic dianhydrideand a polysiloxane diamine and a blend of polyimide compound ofrecurring structural units of the formula: ##STR10## with a polyimide,as required, composed of recurring structural units of the formula:##STR11## wherein the molar proportion of the latter is from 0 to 50 molpercent wherein R is a divalent hydrocarbon radical, R' is a monovalenthydrocarbon radical, R" is a tetravalent organic radical, Q is adivalent silicon-free organic radicalwhich is the residue of an organicdiamine, x is a whole number equal to at least 1 and advantageously from1 to 8 and as high as 1 to 10,000 or more, m is an integer greater than1 n is zero or an integer greater than 0, and at least one layer of aglass material disposed on the layer of protective coating material. 2.The semiconductor element of claim 1 whereinm is from 10 to 10,000 and nis from 1 to 10,000.
 3. The semiconductor element of claim 1 wherein mis
 0. 4. The semiconductor element of claim 3 whereinm is from 10 to10,000.
 5. The semiconductor element of claim 1 whereinthe coefficientof thermal expansion of the glass material approximates the coefficientof thermal expansion of the material of the body.
 6. The semiconductorelement of claim 5 wherein n is
 0. 7. The semiconductor element of claim5 and includinga second layer of glass comprising silicon dioxidedisposed on the at least one layer of glass material.
 8. Thesemiconductor element of claim 5 whereinthe glass material is oneselected from the group consisting of borosilicate glass andphosphosilicate glass.
 9. The semiconductor element of claim 8 andincludinga second layer of glass comprising silicon dioxide disposed onthe at least one layer of glass material.
 10. The semiconductor elementof claim 8 whereinthe thickness of the glass material is from 0.1micrometer to 10 micrometer.
 11. The semiconductor element of claim 10whereinthe thickness of the glass material is 3 micrometers.
 12. Thesemiconductor element of claim 11 and includinga second layer of glasscomprising silicon dioxide disposed on the at least one layer of glassmaterial, and the thickness of the second layer of glass is 2000A. 13.The semiconductor element of claim 12 whereinthe semiconductor materialis silicon.
 14. The semiconductor element of claim 12 whereinthe glassmaterial is borosilicate and comprises from 15 to 25 percent mol of B₂O₃ therein.
 15. The semiconductor element of claim 14 whereinthe glassmaterial comprises 19 ± 2 mol percent B₂ O₃.
 16. The semiconductorelement of claim 15 whereinthe semiconductor material is silicon. 17.The semiconductor element of claim 10 whereinthe glass material isborosilicate and comprises from 15 to 25 mol percent of B₂ O₃ therein.18. The semiconductor element of claim 17 whereinthe semiconductormaterial is silicon.
 19. The semiconductor element of claim 17 whereinmis from 10 to 10,000 and n is from 1 to 10,000.
 20. The semiconductorelement of claim 17 whereinthe glass material comprises 19 ± 2 molpercent B₂ O₃.
 21. The semiconductor element of claim 20 whereinthesemiconductor material is silicon.
 22. The semiconductor element ofclaim 10 and includinga second layer of glass comprising silicon dioxidedisposed on the at least one layer of glass material, and the thicknessof the second layer of glass is from 1000A to 5000A.
 23. Thesemiconductor element of claim 22 whereinthe semiconductor material issilicon.
 24. The semiconductor element of claim 22 whereinthe glassmaterial is borosilicate and comprises from 15 to 25 mol percent of B₂O₃ therein.
 25. The semiconductor element of claim 24 whereinthe glassmaterial comprises 19 ± 2 mol percent B₂ O₃.
 26. The semiconductorelement of claim 25 whereinthe semiconductor material is silicon.